Plano-fresnel LED lens and LED assembly thereof

ABSTRACT

A plano-Fresnel LED lens and a LED assembly thereof are revealed. The lens is a Fresnel lens whose optical surface on the forward side thereof is a plano surface having saw teeth with vertical taper (draft with vertical shape) so that the lens in the LED assembly concentrates light emitted from a LED chip to generate light whose peak intensity is an elliptic distribution pattern. Moreover, the lens and the LED assembly thereof satisfy certain conditions. Thereby, light from the LED chip is gathered by a single lens to form a preset specific distribution pattern and is satisfying requirement of the ratio of the luminous flux that is larger than 85%. The plano-Fresnel LED lens and a LED assembly thereof are applied to lights and flashlights in mobile phones or cameras.

BACKGROUND OF THE INVENTION

The present invention relates to a LED lens and a LED assembly thereof, especially to a Plano-Fresnel LED lens whose peak intensity is an elliptic distribution pattern in a LED assembly, being applied to LED lighting devices, flashlights of mobile phones or cameras.

LED with features of low voltage, low power consumption and long operation life has been broadly applied to indicators, illuminators and so on. Moreover, due to pure light color, compact volume and flat package, LED is also used on flashlight of mobile phones. Yet light emitted from LED chip is a point source with uneven brightness. Thus a lot of studies focus on light collection. Besides minimization of chip size, improvement of light emitting efficiency, the lens used is also an important direction of technical development.

Along with development of modern technology, electronics are getting more miniature, compact and multi-functional. A lot of electronic products such as digital still cameras, PC cameras, network cameras, mobile phones and even personal digital assistant (PDA) are equipped with a lens. The LED lights or flashlight applied to such products are formed by a single or multiple LED array(s). For convenience of easy carrying and humanized design, LED flashlights or lighting devices not only meet requirements of luminous flux such as combinations of LED elements with different distribution patterns but also require miniature and lower cost.

In lens design of LED, there are two types-primary optical lens and secondary optical lens. The primary optical lens is a lens directly packaged on the LED chip and is for concentrating light while the secondary optical lens is an LED array formed by signal chip or a plurality of LED chips for spreading light beams. The conventional design of the primary optical lens is shown in ES2157829, symmetrical aspherical lens is used. Refer to JP3032069, JP2002-111068, JP2005-203499, US2006/187653, and CN101013193, spherical lens is used as primary optical lens.

In JP2002-221658, spherical lens is applied to Bulk-type LED. In high-level applications, the primary optical lens not only concentrates light but also generates specific distribution pattern with even peak intensity such as large angle, small angle, round or elliptic distribution pattern. The primary optical lens is used in combination with the LED array so as to achieve optimal optical effects.

The application of the primary optical lens is shown in FIG. 1A & FIG. 1B. A lens 23 is covered over a LED chip 21. Light emitted from the LED chip 21 passes through the lens 23 to be concentrated to form a preset light pattern. Or a layer of secondary optical lens is added over the primary optical lens for brightness uniformity. There are various designs of the primary optical lens and some of them use a Fresnel optical surface, as revealed in WO/2003/083943, JP2005-049367, U.S. Pat. No. 6,726,859, US2007/0275344, US2008/0158854, EP1091167, and TW200711186 etc.

However, above conventional technique uses Fresnel lens covered over a plurality of LEDs, working as a secondary optical lens like a projector. Due to fast development of LED light emitting efficiency, the applications of a single LED have become more important. In the LED array or light sources formed by a plurality of LEDs, the brightness become in uniformity due to compensation of cross light beams through the lens. As to the single LED, the design of the primary optical lens is more complicated than that of the LED array or light sources formed by multiple LEDs because both the light concentration efficiency and the uniformity of brightness of the primary optical lens should be considered. A set of Fresnel zone plates is disposed on surface of the Fresnel lens and a zone pitch thereof is increasing gradually from the inside to the outside or from the outside to the inside. Besides light guiding and light collection, the Fresnel lens with features of light weight, compact volume and plastic nature and lower cost is suitable for being applied to lighting systems. For example, in JP2005-257953 and US 2006/0027828, a Fresnel lens with a single-side or double-side is disposed over a LED light source so as to generate uniform brightness, as shown in FIG. 1A & FIG. 1B. Refer to TW560085, by a paraboloid surface and a Fresnel lens, reducing the divergent light and uniform brightness may be formed. Furthermore, refer to Korean 1020070096368 and TW 1261654, a LED primary lens is made by a Fresnel lens but the distribution pattern thereof is a round distribution pattern.

However, as to multiple point LED lighting systems, brightness uniformity of both illuminance and light intensity should be considered. Conventional techniques usually use a certain ratio of the zone pitch to the zone height or changing zone pitch with changing zone height. For lighting system formed by a plurality of LEDs, changing zone pitch is better for matching requirements of uniform illuminance/light intensity. As to a single LED primary optical lens, the zone pitch depends on optical properties of the lens. Although the Fresnel lens with complicated surface and higher manufacturing cost, it provides better light efficiency and brightness uniformity, especially being applied to lighting devices with a single LED. In order to make light from single LED achieve higher efficiency, the present invention provide a primary optical lens of the LED made by Fresnel lens so as to concentrate light from surface of the LED chip and generate an elliptic distribution pattern with uniform peak intensity.

SUMMARY OF THE INVENTION

Therefore it is a primary object of the present invention to provide a plano-Fresnel LED lens and a LED assembly thereof. The LED assembly having a LED chip for emitting light, a Fresnel lens fort concentrating light and generating Elliptic distribution pattern with uniform peak intensity and a gel layer filled between the Fresnel lens and the LED chip for sealing. Wherein, the Fresnel lens can be a plano-concave lens whose outer surface is tapered or perpendicular. A concave surface of the Fresnel lens is an optical surface facing the light source and is able to be aspherical or spherical while a plano-Fresnel surface thereof is an optical surface on forward side and is a Fresnel optical surface. Moreover, the light-collecting curved surface (R_(F)) for forming the plano-Fresnel surface can be aspherical or spherical surface and its zone can be draft with vertical shape and equal zone pitch and satisfying the following conditions:

$\begin{matrix} {0.7 \leq \frac{f_{s}}{r_{n}} \leq 2.2} & (1) \\ {0.1 \leq {\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} \leq 1.25} & (2) \\ {{\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} \leq 0.6} & (3) \end{matrix}$ wherein:

$\begin{matrix} {f_{g} = {{\left( {\frac{1}{R_{1}} - \frac{1}{R_{F}}} \right) \cdot f_{s}}}} & (4) \\ {\omega_{x} = {\tan^{- 1}\left( \frac{D}{{d\; 0} + {d\; 1} + {d\; 2} + {Lx}} \right)}} & (5) \\ {\omega_{y} = {\tan^{- 1}\left( \frac{D}{{d\; 0} + {d\; 1} + {d\; 2} + {Ly}} \right)}} & (6) \end{matrix}$ Wherein f_(s) is effective focal length of the lens, r_(n) is radius of a last zone of a Fresnel optical surface R2, d₂ is thickness of the lens on a central axis Z, N_(d2) is refractive index of the lens, 2φ_(x) (deg.) is an angle of a half of highest light intensity (I_(1/2)) in the X direction of the light emitted from the lens, 2φ_(y) (deg.) is an angle of a half of highest light intensity (I_(1/2)) in the Y direction of the light emitted from the lens, 2Lx is length of the LED chip in the X direction, 2Ly is length of the LED chip in the Y direction, fg is a relative focal length of the lens, R₁ is a radius of an optical surface on the source side, R_(F) is a radius of a plano-Fresnel surface on the forward side, d₀ is thickness of the LED chip, d₁ is thickness of a gel layer on the central axis, D is radius of an optical surface on the forward side.

Moreover, in order to meet various requirements of distribution pattern and light concentration properties, the radius R_(F) of the light-collecting curved surface (R_(F)) (a convex surface) for forming the plano-Fresnel surface of the Fresnel lens can be set as a radius of a spherical surface or an aspherical surface.

In order to simplify the manufacturing of the device, the plano-concave Fresnel lens can be replaced to be a plano-plano lens made from optical material whose forward-side optical surface is a plano-Fresnel surface and is satisfying from equation (1) to equation (3). Where the optical material may be selected by plastic resin or glass.

In order to improvement concentrating efficiency of LED assembly, the outer surface of the Fresnel lens may be tapered with taper ν whose forward-side optical surface is a Fresnel convex surface and is satisfying from equation (1) to equation (3).

It is another object of the present invention to provide a LED assembly that includes a plano-concave or a plano-plano Fresnel LED lens and a LED chip and the LED assembly features on its elliptic distribution pattern and the ratio of luminous flux is larger than 85% (η=β/α≧85%) and is satisfying the following conditions: E _(1/2)≦0.6E _(d)  (7) wherein

$\begin{matrix} {E_{1/2} = {\frac{I_{1/2}}{\left( {\pi\;{r_{n} \cdot \sin}\;\phi_{x}} \right) \cdot \left( {{r_{n} \cdot \sin}\;\phi_{y}} \right)} \cdot \eta}} & (8) \end{matrix}$ wherein r_(n) is radius of a last zone of the Fresnel surface R2, α is luminous flux of the LED chip, β is luminous flux at infinity (100×f_(s)) of the forward side without consideration of attenuation, η is ratio of the luminous flux, E_(d) is incidence of the LED chip, and E_(1/2) is incidence at the half of highest light intensity from the Fresnel lens surface.

The plano-Fresnel LED lens and the LED assembly thereof according to the present invention have elliptic distribution pattern and satisfies the requirement of luminous flux larger than 85%. Moreover, the thickness of the lens is minimized so that the lens can be applied to a single LED, LED arrays for lighting, or flashlights on mobile phones and cameras.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows LED assembly of a conventional LED lens;

FIG. 1B shows LED assembly of a conventional LED lens;

FIG. 2 is a perspective view of LED assembly of a Fresnel LED lens without taper according to the present invention;

FIG. 3 is a perspective view of LED assembly of a Fresnel LED lens with taper according to the present invention;

FIG. 4 shows a relationship between the radius of a convex surface and a plano-Fresnel surface of a Fresnel LED lens having draft with vertical shape and equal zone pitch;

FIG. 5 shows a relationship between the radius of a convex surface and a plano-Fresnel surface of a Fresnel LED lens having draft with vertical shape and equal zone height;

FIG. 6 is a schematic drawing showing LED assembly of an embodiment according to the present invention;

FIG. 7 is a schematic drawing showing taper of a Fresnel LED lens of an embodiment according to the present invention;

FIG. 8 shows light paths of LED assembly of an embodiment according to the present invention;

FIG. 9 shows refraction of group A light beams and group B light beams by a Fresnel LED lens;

FIG. 10 shows light path of group A light beams and group B light beams passing through a Fresnel LED lens;

FIG. 11 is a schematic drawing uniform light intensity formed by combination of group A light beams with group B light beams in FIG. 9 & FIG. 10;

FIG. 12 shows relationship between light intensity distribution of the first embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 13 shows relationship between light intensity distribution of the second embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 14 shows relationship between light intensity distribution of the third embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 15 shows relationship between light intensity distribution of the fourth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 16 shows relationship between light intensity distribution of the fifth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 17 shows relationship between light intensity distribution of the sixth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 18 shows relationship between light intensity distribution of the seventh embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 19 shows relationship between light intensity distribution of the eighth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 20 shows relationship between light intensity distribution of the ninth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 21 shows relationship between light intensity distribution of the tenth embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 22 shows relationship between light intensity distribution of the eleventh embodiment of the LED assembly and grazing angle in a polar coordinate system light;

FIG. 23 shows relationship between light intensity distribution of the twelfth embodiment of the LED assembly and grazing angle in a polar coordinate system light; and

FIG. 24 shows relationship between light intensity distribution of the thirteenth embodiment of the LED assembly and grazing angle in a polar coordinate system light.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Refer to FIG. 6, a LED assembly 10 according to the present invention comprises a LED chip 11, a gel layer 12 and a lens 13 along a central axis Z from a source side to a forward side. When light is emitted from the LED chip 11, passing through the gel layer 12 and being concentrated by the lens 13 to form a light beam with elliptic distribution pattern symmetrical to the central axis Z that projects onto the forward side. The lens 13 is made of optical material such as optical glass or optical plastic resin. A concave surface of the lens 13 is a source-side optical surface R1 facing on the light source and is aspherical or spherical optical surface. The other side opposite to the concave surface is a plano-Fresnel optical surface R2 with draft with vertical shape and facing on the forward side. The plano-Fresnel optical surface R2, the lens thickness d₂ and the effective focal length f_(s) of the lens 13 satisfy the equation (1) and the equation (2). The angle 2φ (having 2φ_(x) in the X direction and 2φ_(y) in the Y direction) of distribution pattern of light intensity formed by the lens 13 satisfies the equation (3).

The material of the gel layer 12 is not restricted. In the LED assembly, optical resin or silicon gel is commonly used.

Refer to FIG. 2, the LED assembly 10 is a plano-Fresnel LED lens 13. An optical surface R1 of the lens 13 on source side is a flat surface (R1=∞) while the other optical surface R2 (opposite surface) on forward side is a plano-Fresnel optical surface with vertical shape draft.

Refer to FIG. 3, a further embodiment of the LED assembly 20 is revealed. Along with the central axis Z from the source side to the forward side, the LED assembly 20 comprises of a LED chip 21, a gel layer 22 and a plano-Fresnel lens 23. The difference between this LED assembly 20 and the LED assembly 10 in FIG. 2 is in that an outer surface of the lens 23 is with taper ν, as shown in FIG. 7 so as to reduce divergent from the side surface of the lens 23 and improve the optical efficiency.

The forward-side optical surface R2 of the lens 13 or the lens 23 of the invention is a plano-Fresnel optical surface having draft with vertical shape, as shown in FIG. 4 & FIG. 5. The Fresnel optical surface R2 is transformed by the radius of R_(F). By means of different ways of transformation the radius of R_(F), various Fresnel optical surface R2 are formed, as equal zone pitch (FIG. 4) and equal zone height (FIG. 5).

Refer to FIG. 4, a plano-Fresnel optical surface R2 with equal zone pitch is shown. The zone pitch r_(t) thereof is a fixed value. The light optical surface with radius of R_(F) is transformed into a multi-zone plano-Fresnel optical surface R2 by equal zone pitch r_(t) but with unequal zone height h_(d) (FIG. 6). Refer to FIG. 5, a plano-Fresnel optical surface R2 with equal zone height is shown. That means the zone height h_(d) is a fixed value. The optical surface with radius of R_(F) is transformed into a multi-zone Fresnel optical surface R2 by equal vertical zone height h_(d) but with unequal zone pitch r_(t).

Each zone on the forward-side plano-Fresnel optical surface R2 is formed by a slope and a vertical zone surface (ring-shaped surface) so that the zone is called draft with vertical shape. The radius of the first zone is r₁ and the radius of the last zone is r_(n). As shown in FIG. 9, when light emits into the plano-Fresnel optical surface R2, the light is refracted by the slope of each zone so as to achieve similar optical effects of paraboloid optical surface.

Refer from FIG. 9 to FIG. 11, after being refracted by the Fresnel optical surface R2, the angles of emergence φ of the group A light beams (such as A1, A2, A3 light beam) on an object are different due to different incident angles of the light beams A1, A2, A3, as shown in FIG. 10. On the position parallel to the central axis toward vertical direction, the group A light beams have higher light intensity in the center thereof. Similarly, after being refracted by the plano-Fresnel optical surface, a light-beam group B (such as B1, B2, B3 light beam) is also a light-beam group whose light intensity is higher in the center thereof. By the combinations of group A and group B, as shown in FIG. 11, a light pattern with even light intensity is generated so as to improve brightness uniformity.

If the optical surface R1 of the lens 13 or the lens 23 is formed by aspherical optical surface, the Aspherical Surface Formula is the equation (9):

$\begin{matrix} {Z = {\frac{{ch}^{2}}{1 + \sqrt{\left( {1 - {\left( {1 + K} \right)c^{2}h^{2}}} \right)}} + {A_{4}h^{4}} + {A_{6}h^{6}} + {A_{8}h^{8}} + {A_{10}h^{10}}}} & (9) \end{matrix}$ wherein c is curvature, h is height of the lens, K is conic constant, and A₄ to A₁₀ respectively are Nth Order Aspherical Coefficients.

The curvature radius of R_(F) of the plano-Fresnel optical surface R2 is also defined by the equation (9), wherein Conic Constant of the curvature radius R_(F) of the paraboloid for collecting light is −1 (K=−1) for paraboloid surface, is 0 (K=0) for spherical surface, respectively.

Refer to FIG. 8, light from the LED chip 11 (21) is concentrated and refracted by the lens 13 (23) to form a required elliptic distribution pattern that satisfies the condition of β/α≧85% at an angle of 2φ (2φ_(x) in the X direction and 2φ_(y) in the Y direction). Neglecting attenuation such as air refraction and scattering, the equation (7) is satisfied. Therefore, by a plano-concave or plano-plano Fresnel LED lens and a LED chip, the LED assembly 10 (20) can emit preset Elliptic distribution pattern with uniform light intensity. Moreover, the LED assembly can be used in the form of a single assembly or an array formed by the LED assemblies with different distribution patterns.

In an embodiment of the present invention, the LED chip 11 is a blu-ray whose size is 1.85×0.77 mm, 1st peak wave-length is 450 nm, and 2nd peak wave-length is 550 nm. The blue light has diverge angle of ω_(x)=39.8° in the X direction and ω_(y)=35.2° in the Y direction for last light beam, α=78.5 lm, and light intensity E_(d)=23.97 Lux. The diameter of the lens 13(23) is 5 mm (D=2.5 mm). The optical surface on the forward side R2 is a Fresnel optical surface having vertical shape, and equal zone height/or equal zone pitch. The gel layer 12 is made from transparent optical silicon gel with refractive index of 1.491. As to the LED assembly with a primary optical lens, other components except the lens and LED assembly of the present invention are obvious to those in the art. Thus the size and material of the components, wavelength and emitting angle of LED, patterns, the zone pitch and the zone height of the Fresnel optical surfaces all can be changed, modified and even substituted with equal effect parts.

As to the following thirteen embodiments, in the first to seventh embodiments, a LED assembly with a plano-plano Fresnel lens that is with no taper and equal zone height is used. In the eighth and ninth embodiments, a LED assembly with a plano-plano Fresnel lens that is with taper and equal zone height is used. In the tenth and eleventh embodiments, a LED assembly with a plano-plano Fresnel lens that is with no taper and equal zone pitch is used. In the twelfth and thirteenth embodiments, a LED assembly with a plano-concave Fresnel lens that is with no taper and equal zone height is used.

Two tables are shown in the following each embodiment respectively, wherein the first table includes data of curvature radius R (unit: mm) of the source-side optical surface R1 as well as that of the optical surface on the source side R2, or curvature radius R_(F) (unit: mm), along a central axis Z from the source side to the forward side, the on-axis surface spacing di (unit: mm), the taper ν of the lens (13˜23), respective refractive index (N_(d)) and the optical surface number. Denoted that labeled with * is an aspherical Fresnel optical surface. The second table is shown the respective parameters in the equation (9) of the aspherical Fresnel optical surface, radius r₁ of a first Fresnel zone from the center of the lens, radius r_(n) of the last Fresnel zone, Fresnel zone height h_(d) and number of Fresnel zones.

The First Embodiment Refer to FIG. 6, FIG. 12

TABLE ONE fs = 2.024 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.000 2.00 1.582 *Aspherical Zone Fesnel

TABLE TWO K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface 0.1 0.447 2.490 31 (mm)

In this embodiment, the lens 13 is made from glass with refractive index Nd2 of 1.582 and Abbe number νd2 of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 68° in the X direction, 30° in the Y direction and the luminous flux β=69.201 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7):

η = 0.8815 I_(1/2) = 33.5 ϕ_(x) = 32.5 ϕ_(y) = 15.2 $\frac{f_{s}}{r_{n}} = 0.8130$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.5751$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2394$ $\frac{E_{1/2}}{E_{d}} = 0.4489$

By the above table one and table two as well as FIG. 12, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Second Embodiment Refer to FIG. 6 & FIG. 13

TABLE THREE f = 2.530 υ = 0 Surface No. R or R_(F) d_(i) Nd_(i) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE FOUR K A₂ A₄ A₆ Aspherical −8.5000E−01 0.0000E+00 2.4000E−05 5.7000E−08 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface 0.1 0.499 2.480 30 (mm)

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 68° in the X direction, 33° in the Y direction and the luminous flux β=70.245 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7):

η = 0.8948 I_(1/2) = 32.5 ϕ_(x) = 33.7 ϕ_(y) = 16.8 $\frac{f_{s}}{r_{n}} = 1.0203$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 1.1410$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.1319$ $\frac{E_{1/2}}{E_{d}} = 0.3915$

By the above table three and table four as well as FIG. 13, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Third Embodiment Refer to FIG. 6 & FIG. 14

TABLE FIVE fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE SIX K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface 0.06 0.387 2.510 42 (mm)

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 64° in the X direction, 36° in the Y direction and the luminous flux β=69.816 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7):

η = 0.8893 I_(1/2) = 30.0 ϕ_(x) = 32.1 ϕ_(y) = 18.1 $\frac{f_{s}}{r_{n}} = 1.0081$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4601$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2108$ $\frac{E_{1/2}}{E_{d}} = 0.3406$

By the above table five and table six as well as FIG. 14, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Fourth Embodiment Refer to FIG. 6 & FIG. 15

TABLE SEVEN f = 2.530 υ = 0 Surface No. R or R_(F) d_(i) Nd_(i) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.491 *Aspherical Zone Fesnel

TABLE EIGHT K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface 0.06 0.387 2.510 41 (mm)

In this embodiment, the lens 13 is made from PMMA plastic with refractive index N_(d2) of 1.491 and Abbe number ν_(d2) of 32. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 68° in the X direction, 43° in the Y direction and the luminous flux β=72.48 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.9233 I_(1/2) = 23.5 ϕ_(x) = 34.0 ϕ_(y) = 21.5 $\frac{f_{s}}{r_{n}} = 1.0081$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.3881$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.1672$ $\frac{E_{1/2}}{E_{d}} = 0.2231$

By the above table seven and table eight as well as FIG. 15, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Fifth Embodiment Refer to FIG. 6 & FIG. 16

TABLE NINE fs = 5.061 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 2.500 2.00 1.582 *Spherical Zone Fesnel

TABLE TEN r_(t) r_(n) No. of Zone Fesnel Surface 0.0625 2.500 41 (mm)

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern 68° in the X direction, 43° in the Y direction and the luminous flux β=72.48 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8980 I_(1/2) = 22.5 ϕ_(x) = 43.0 ϕ_(y) = 34.5 $\frac{f_{s}}{r_{n}} = 2.0243$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.2300$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.4536$ $\frac{E_{1/2}}{E_{d}} = 0.1111$

By the above table nine and table ten as well as FIG. 16, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Sixth Embodiment Refer to FIG. 6 & FIG. 17

TABLE ELEVEN fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 4.96 1.582 *Aspherical Zone Fesnel

TABLE TWELVE K A₂ A₄ A₆ Aspherical −9.0000E−01 0.0000E+00 2.4000E−05 5.7000E−08 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.387 2.478 46

In this embodiment, the lens 13 is made from glass with refractive index Nd2 of 1.582 and Abbe number νd2 of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern 68° in the X direction, 43° in the Y direction and the luminous flux β=72.48 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8913 I_(1/2) = 32.5 ϕ_(x) = 31.0 ϕ_(y) = 17.0 $\frac{f_{s}}{r_{n}} = 1.0213$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 1.1401$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.1030$ $\frac{E_{1/2}}{E_{d}} = 0.4161$

By the above table eleven and table twelve as well as FIG. 17, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Seventh Embodiment Refer to FIG. 6 & FIG. 18

TABLE THIRTEEN fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 4.99 1.582 *Aspherical Zone Fesnel

TABLE FOURTEEN K A₂ A₄ A₆ Aspherical −1.1000E+00 0.0000E+00 2.4000E−05 5.7000E−08 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.388 2.494 38

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 65° in the X direction, 40° in the Y direction and the luminous flux β=69.33 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8832 I_(1/2) = 27.5 ϕ_(x) = 33.7 ϕ_(y) = 19.5 $\frac{f_{s}}{r_{n}} = 1.0146$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 1.1475$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.1252$ $\frac{E_{1/2}}{E_{d}} = 0.2799$

By the above table thirteen and table fourteen as well as FIG. 18, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Eighth Embodiment Refer to FIG. 6 & FIG. 19

TABLE FIFTEEN fs = 2.530 υ = 3.505 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE SIXTEEN K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.387 2.387 37

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 65° in the X direction, 60° in the Y direction and the luminous flux β=69.588 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8976 I_(1/2) = 22.0 ϕ_(x) = 37.5 ϕ_(y) = 27.0 $\frac{f_{s}}{r_{n}} = 1.0598$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4601$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2176$ $\frac{E_{1/2}}{E_{d}} = 0.3022$

By the above table fifteen and table sixteen as well as FIG. 19, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Ninth Embodiment Refer to FIG. 6 & FIG. 20

TABLE SEVENTEEN fs = 2.530 υ = 7.172 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE EIGHTEEN K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.387 2.258 33

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 68° in the X direction, 33° in the Y direction and the luminous flux β=71.267 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.9078 I_(1/2) = 34.0 ϕ_(x) = 33.8 ϕ_(y) = 16.8 $\frac{f_{s}}{r_{n}} = 1.2045$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4601$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2176$ $\frac{E_{1/2}}{E_{d}} = 0.4998$

By the above table seventeen and table eighteen as well as FIG. 20, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Tenth Embodiment Refer to FIG. 6 & FIG. 21

TABLE NINETEEN fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE TWENTY K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface r_(t) r_(n) No. of Zone Fesnel Surface (mm) 0.5 2.500 5

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 68° in the X direction, 70° in the Y direction and the luminous flux β=72.056 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.9214 I_(1/2) = 26.0 ϕ_(x) = 40.5 ϕ_(y) = 35.0 $\frac{f_{s}}{r_{n}} = 1.0121$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4601$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.0081$ $\frac{E_{1/2}}{E_{d}} = 0.1366$

By the above table nineteen and table twenty as well as FIG. 21, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Eleventh Embodiment Refer to FIG. 6 & FIG. 22

TABLE TWENTY-ONE fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 ∞ 0.52 1.410 S2* 1.250 2.00 1.582 *Aspherical Zone Fesnel

TABLE TWENTY-TWO K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface r_(t) r_(n) No. of Zone Fesnel Surface (mm) 0.0625 2.500 40

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 60° in the X direction, 80° in the Y direction and the luminous flux β=72.164 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.9192 I_(1/2) = 30.0 ϕ_(x) = 39.4 ϕ_(y) = 30 $\frac{f_{s}}{r_{n}} = 1.0121$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4601$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.1147$ $\frac{E_{1/2}}{E_{d}} = 0.2184$

By the above table twenty-one and table twenty-two as well as FIG. 22, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Twelfth Embodiment Refer to FIG. 6 & FIG. 23

TABLE TWENTY-THREE fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 30.00 0.62 1.410 S2* 1.250 1.90 1.582 *Aspherical Zone Fesnel

TABLE TWENTY-FOUR K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.387 2.510 42

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 60° in the X direction, 40° in the Y direction and the luminous flux β=69.506 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8854 I_(1/2) = 30.0 ϕ_(x) = 33.1 ϕ_(y) = 19.0 $\frac{f_{s}}{r_{n}} = 1.0008$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.4361$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2053$ $\frac{E_{1/2}}{E_{d}} = 0.2188$

By the above table twenty-three and table twenty-four as well as FIG. 23, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention.

The Thirteenth Embodiment Refer to FIG. 6 & FIG. 24

TABLE TWENTY-FIVE fs = 2.530 υ = 0 Surface No. R or R_(F) d_(i) N_(di) S0 ∞ 0.10 S1 9.00  0.87 1.410 S2* 1.250 1.65 1.582 *Aspherical Zone Fesnel

TABLE TWENTY-SIX K A₂ A₄ A₆ Aspherical −1.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 Surface h_(d) r₁ r_(n) No. of Zone Fesnel Surface (mm) 0.06 0.387 2.510 35

In this embodiment, the lens 13 is made from glass with refractive index N_(d2) of 1.582 and Abbe number ν_(d2) of 61.7. The light is concentrated by the lens 13 to form an elliptic distribution pattern, 60° in the X direction, 40° in the Y direction and the luminous flux β=69.506 lm at infinity (100×f_(s)) without consideration of air refraction and scattering. The following values satisfy the equation (1), equation (2), equation (3) and equation (7).

η = 0.8828 I_(1/2) = 29.0 ϕ_(x) = 31.0 ϕ_(y) = 20.2 $\frac{f_{s}}{r_{n}} = 1.0081$ ${\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} = 0.3786$ ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} = 0.2227$ $\frac{E_{1/2}}{E_{d}} = 0.2103$

By the above table twenty-five and table twenty-six as well as FIG. 24, it has been proved that the LED assembly with plano-Fresnel LED lens of the invention can achieve higher efficiency and generate an elliptic distribution pattern with uniform peak intensity so as to increase the application of the invention. 

1. A plano-Fresnel LED (Light emitting diode) lens, applied to a LED assembly having a LED chip, a gel layer and a lens along a central axis from a source side to a forward side, comprising: an optical surface on the forward side and an optical surface on the source side; wherein the optical surface on forward side is a plano-Fresnel optical surface with vertical draft so as to make light from the LED chip pass through the gel layer, the lens and form an elliptic distribution pattern on the forward side, and the lens satisfies conditions of: $0.7 \leq \frac{f_{s}}{r_{n}} \leq 2.2$ $0.1 \leq {\left( {N_{d\; 2} - 1} \right)\frac{d_{2}}{f_{s}}} \leq 1.25$ wherein f_(s) is effective focal length, r_(n) is radius of a last zone of a Fresnel optical surface, d₂ is thickness of the lens on a central axis, and N_(d2) is refractive index of the lens.
 2. The plano-Fresnel LED lens as claimed in claim 1, wherein the lens further satisfies following conditions: ${\sqrt{\left( \frac{\phi_{x} - \omega_{x}}{\pi} \right)^{2} + \left( \frac{\phi_{y} - \omega_{y}}{\pi} \right)^{2}} \cdot f_{g}} \leq 0.6$ wherein: $f_{g} = {{\left( {\frac{1}{R_{1}} - \frac{1}{R_{F}}} \right) \cdot f_{s}}}$ $\omega_{x} = {\tan^{- 1}\left( \frac{D}{{d\; 0} + {d\; 1} + {d\; 2} + {Lx}} \right)}$ $\omega_{y} = {\tan^{- 1}\left( \frac{D}{{d\; 0} + {d\; 1} + {d\; 2} + {Ly}} \right)}$ wherein f_(s) is effective focal length of the lens, 2φ_(x)(deg.) is an angle of a half of highest light intensity (I_(1/2)) in the X direction of the light emitted from the lens, 2φ_(y) (deg.) is an angle of a half of highest light intensity (I_(1/2)) in the Y direction of the light emitted from the lens, 2Lx is length of the LED chip in the X direction, 2Ly is length of the LED chip in the Y direction, fg is a relative focal length of the lens, R₁ is a radius of an optical surface on the source side, R_(F) is a radius of a fresnel convex surface on the forward side, d_(o) is thickness of the LED chip, d₁ is thickness of a gel layer on the central axis, d₂ is thickness of the lens on a central axis, D is radius of an optical surface on the forward side.
 3. The plano-Fresnel LED lens as claimed in claim 1, wherein the optical surface on the source side is a flat surface or a concave surface.
 4. The plano-Fresnel LED lens as claimed in claim 1, wherein the Fresnel optical surface is with equal zone height or with equal zone pitch.
 5. The plano-Fresnel LED lens as claimed in claim 1, wherein an outer surface of the lens is with taper.
 6. The plano-Fresnel LED lens as claimed in claim 1, wherein the lens is made from glass optical material or plastic optical material.
 7. A LED assembly along a central axis from a source side to a forward side comprising: a LED chip, a gel layer and a plano-Fresnel LED lens of claim 1; wherein the LED assembly generates an elliptic distribution pattern and satisfies conditions of: E_(1/2) ≤ 0.6E_(d); ${{{wherein}\mspace{14mu} E_{1/2}} = {\frac{I_{1/2}}{\left( {\pi\;{r_{n} \cdot \sin}\;\phi_{x}} \right) \cdot \left( {{r_{n} \cdot \sin}\;\phi_{y}} \right)} \cdot \eta}};$ wherein r_(n) is radius of a last zone of the Fresnel optical surface, 2φ_(x) (deg.) is an angle of a half of highest light intensity (I_(1/2)) in the X direction of the light emitted from the lens, 2φ_(y) (deg.) is an angle of a half of highest light intensity (I_(1/2)) in the Y direction of the light emitted from the lens α is luminous flux of light emitted from the LED chip, β is luminous flux of light at infinity (100×f_(s)) on the forward side without consideration of attenuation, η is ratio of the luminous flux−η=β/α, E_(d) is illumination of the LED chip.
 8. The LED assembly as claimed in claim 7, wherein the ratio of luminous flux of light emitted from the LED chip to luminous flux of light at infinity on the forward side satisfies: β/α≧85% wherein α is luminous flux of light emitted from the LED chip, and β is the luminous flux of light at infinity on the forward side of the LED assembly, neglecting air refraction and scattering. 